Like most genitourinary anomalies, vesicoureteral reflux appears to have a multifactorial origin, although a genetic component undoubtedly exists. Siblings of patients with reflux have a much greater risk of having reflux than the normal population. Up to 50% of siblings have been noted to have reflux. Notably, the large majority (75%) are asymptomatic. Contrary to the findings in some earlier studies, there appears to be no relationship between the grade of reflux in index patients and that in their siblings. The presence of renal scars in the index case is probably also less important than was once supposed. The proposed clinical study aims to identify the critical region involved in vesicoureteral reflux and identify additional genes in the region; to establish a repository of DNA and blood samples from patients with reflux and their family members for the purpose of linkage and mutational analysis; and to determine the presence or absence of deletions of chromosomes in these individuals and determine the size and location of identified deletions/mutations. Blood samples will be obtained from patients and their immediate family during a clinic visit. The amount of blood drawn will depend on the age of the subject, and will be an amount appropriate for the isolation of DNA and RNA. Molecular genetic analysis will be performed in the Children's Hospital Genome Mapping Facility. Samples will be aliquoted for DNA extraction and possible establishment of immortalized cell lines. Pedigree information will be obtained.